Different species have different jobs within their community. Some are the farmers, some are traders, some are the janitors, and others have different roles.

Biological Communities

A
population
consists of all individuals of a single
species
that exist together at a given place and time. A species is a single type of organism that can interbreed and produce fertile offspring. All of the populations living together in the same area make up a
community
.

An
ecosystem
is made up of the living organisms in a community and the nonliving things, the physical and chemical factors, that they interact with. The living organisms within an ecosystem are its
biotic
factors (
Figure
below
). Living things include bacteria, algae, fungi, plants, and animals, including invertebrates, animals without backbones, and vertebrates, animals with backbones.

(a) The horsetail Equisetum is a primitive plant. (b) Insects are among the many different types of invertebrates. (c) A giraffe is an example of a vertebrate.

Physical and chemical features are
abiotic
factors. Abiotic factors include resources living organisms need, such as light, oxygen, water, carbon dioxide, good soil, and nitrogen, phosphorous, and other nutrients. Nutrients cycle through different parts of the ecosystem and can enter or leave the ecosystem at many points. Abiotic factors also include environmental features that are not materials or living things, such as living space and the right temperature range. Energy moves through an ecosystem in one direction.

Niches

Organisms must make a living, just like a lawyer or a ballet dancer. This means that each individual organism must acquire enough food energy to live and reproduce. A species' way of making a living is called its
niche
. An example of a niche is making a living as a top carnivore, an animal that eats other animals, but is not eaten by any other animals (
Figure
below
). Every species fills a niche, and niches are almost always filled in an ecosystem.

The top carnivore niche is filled by lions on the savanna, wolves in the tundra, and tuna in the oceans.

Habitat

An organism’s
habitat
is where it lives (
Figure
below
). The important characteristics of a habitat include climate, the availability of food, water, and other resources, and other factors, such as weather.

Birds living in a saguaro cactus. A habitat may be a hole in a cactus or the underside of a fern in a rainforest. It may be rocks and the nearby sea.

Summary

All of the individuals of a species that exist together at a given place and time make up a population. A community is made up of all of the populations in an area.

The living and nonliving factors that living organisms need plus the communities of organisms themselves make up an ecosystem.

A habitat is where an organism lives and a niche is what it does to make a living.